In order to show a real image in the nature from a display, first of all, the real image needs to be converted into a digital image acceptable to the display, the digital image is a digitalized image that is represented, in terms of space, as a limited number of image pixels distributed discretely and, in terms of color, as a limited number of color values (the color values are a red value, a green value, and a blue value) distributed discretely. After the real image is converted into the digital image, there is still a need to drive a plurality of sub-pixels arranged in an array in the display according to the digital image, so as to show the real image from the display.
In the conventional sub-pixel driving method, as shown in FIG. 1, one red sub-pixel, one green sub-pixel, and one blue sub-pixel in a dotted frame constitute one screen pixel, and one screen pixel is used to correspondingly display one image pixel. At the time of displaying, taking that a screen pixel “A” displays an image pixel “a” as an example, a red sub-pixel 1, a green sub-pixel 3, and a blue sub-pixel 2 of the screen pixel “A” are loaded with a red value, a green value, and a blue value of the image pixel “a”, respectively, so as to complete displaying of the image pixel “a”. It can be seen that when displaying by adopting the conventional sub-pixel driving method, one sub-pixel is used to display a corresponding color of one image pixel. For the aim of displaying more image pixels, that is, improving resolution of the display, there is a need to increase the number of sub-pixels on the screen. However, because of limits of manufacturing process, when the number of sub-pixels on the screen reaches a certain extent, it is hard to continue increasing the number of sub-pixels on the screen, when it reaches a certain extent, which results in the fact that it is hard to continue improving resolution of the display.
A sub-pixel rendering method may be adopted to increase resolution of the display without increasing the number of sub-pixels on the screen of the display. In the sub-pixel rendering method, as shown in FIG. 2, one red sub-pixel, one green sub-pixel, and one blue sub-pixel in a dotted frame constitute one screen pixel, and one screen pixel is used to correspondingly display one image pixel. What is different from the conventional sub-pixel driving method is: adjacent screen pixels share sub-images at the time of displaying. Explanation is provided by taking that a screen pixel C and a screen pixel D share the blue sub-pixel 2 as an example. The screen pixel C corresponds to the image pixel “m”, and the screen pixel D corresponds to the image pixel “n”. When data is loaded, a red value and a green value of the image pixel “m” are loaded onto the red sub-pixel 1 and the green sub-pixel 3 respectively; a red value and a green value of the image pixel “n” are loaded onto the red sub-pixel 4 and the green sub-pixel 5 respectively; and an average of a blue value of the image pixel “m” and a blue value of the image pixel “n” is loaded onto the blue sub-pixel 2. When an array of sub-pixels is lightened, through the light mixing effect, the screen pixel C and the screen pixel D complete displaying of the image pixel “m” and the image pixel “n”, respectively, so that sharing of the blue sub-pixel 2 is achieved. It can be known from the above that, by adopting the sub-pixel rendering method, sub-pixel sharing between adjacent screen pixels can be achieved, so that when displaying the same number of image pixels, adopting the sub-pixel rendering method saves the number of sub-pixels used in comparison to the conventional sub-pixel driving method. In other words, when there are the same number of sub-pixels on the screen, by adopting the sub-pixel rendering method, it is possible for the display to attain a higher resolution in comparison to the conventional sub-pixel driving method.
However, since color at a boundary region of the digital image changes relatively fast, a problem of distortion in the boundary region of a displayed image arises when adopting the sub-pixel rendering method. The reason for this distortion problem are as follows: the image pixel “m” and the image pixel “n” are two adjacent image pixels located in the boundary region of the digital image, and a difference of blue value between the image pixel “m” and the image pixel “n” is relatively large; when the image pixel “m” and the image pixel “n” are displayed respectively by the screen pixel C and the screen pixel D shown in FIG. 2, the blue value of the image pixel “m” and the blue value of the image pixel “n” are both presented by the blue sub-pixel 2; thus, in the displayed image, the screen pixel C and the screen pixel D cannot accurately display a difference of blue color between the image pixel m and the image pixel n, which results in the fact that the displayed image cannot accurately show an original contrast in the boundary region of the digital image, leading to distortion in the boundary region of the displayed image.